Coenogonium isidiiferum (Lücking) Lücking, Lichenologist

Kalb, Jutarat, Boonpragob, Kansri & Kalb, Klaus, 2016, New Coenogonium species (Ostropales: Coenogoniaceae) from Thailand, new reports and a revised key to the species occurring in the country, Phytotaxa 283 (2), pp. 101-122 : 113-114

Coenogonium isidiiferum (Lücking) Lücking, Lichenologist 33 (3): 201 (2001). ( Figs. 5B , 7C, 7D )

Dimerella isidiifera Lücking, Lichenologist 31 (4): 367 (1999).— Coenogonium disciforme Papong, Boonpragob & Lücking, Lichenologist 39 (1): 47 (2007).

Thallus crustose, foliicolous, continuous in center, laciniate at margins, thin, smooth, green to greyish green, 5–30

mm diam., without a distinct corticiform layer; prothallus absent. Thallodiscs numerous, 0.15–0.25 mm diam., discshaped, shortly stalked, probably produced at the center of the thallus but soon become detached leaving regular holes. Photobiont Trentepohlia , cells angular to rounded, mostly in irregular plates, partly short threads, cells 8–12 × 4–10 μm. Apothecia rare, epiphyllous, sessile, scattered, rounded, 0.1–0.8 mm diam., 100–180 μm high; disc slightly concave to plane, pale yellow to yellow. Margin thin, distinct, smooth, ± raised above the level of disc, concolorous or paler than disc. Excipulum well-developed, paraplectenchymatous, 15–80 μm broad, colorless, I−. Hypothecium 10–15 μm high, colorless, I−, KI−. Hymenium 25–60 μm high, colorless, I−, KI−. Paraphyses unbranched, 1– 1.4 μm thick, with thickened apices (to 2.5 μm). Asci cylindrical, 22–55 × 3–4 μm, thin walled, without tholus. Ascospores 8 per ascus, irregularly biseriate, narrowly ellipsoid, 1-septate, 6–8 × 2–2.5 μm, 3–4 times as long as broad. Pycnidia not observed. Chemistry: no substances detected by TLC.

Distribution and habitat:—At present known from Thailand (holotype of C. disciforme ), Costa Rica (holotype of C. isidiiferum ), Mexico, Guyana, Ecuador, Argentina, Vietnam and several collections from Queensland, Australia, where it grows in the understory of disturbed remnants of tropical rainforests or ± pristine rainforests from 50– 750 m.

Remarks:—The formation of the thallodiscs is not fully understood. Often they resemble the schizodiscs of some Stegobolus species. In some cases, they seem to develop singularly in front of the laciniae and distinctly separated from the main part of the thallus. These vegetative propagules have been called isidia by Lücking (1999, 2001) and Papong et al. (2007), but true isidia should be completely corticate, which is not the case—they lack a cortex on the lower side. Despite of lacking ascomata and pycnidia, this species is very distinctive and could not be confused with any other member of the genus. There are no differences in the descriptions of C. isidiiferum and C. disciforme . The regular, round holes in the thallus of C. isidiiferum formed after detachment of the thallodiscs can be clearly seen in figures 1A and 1B in Lücking (1999). Therefore, we synonymize the two species. As only a few fertile species have been reported worldwide, we have taken the descriptions of the apothecia (of C. disciforme ) from Nguyen et al. (2011) and (of C. isidiiferum ) from Lücking (2008). The statement of the first authors of a I–, KI– hymenium however seems highly unlikely, as it has not been observed in any other species of the genus..

Material examined:— THAILAND. Nakhon Ratchasima Province: in a tropical rainforest along trail from Nhong Prue to Check Point 19 khao Leam substation, 820 m, 14°26’01.1’’ N, 101°25’01.8’’ E, 23 April 2000, K. Papong RU-19006-1 ( RAMK 007039). AUSTRALIA. Queensland: Atherton Tableland, foothills of Mount Lewis, Julatten between Mount Molloy and Mossman, Kingfisher Lodge, in very disturbed remnants of a tropical rainforest, 420 m, 16°35’44’’ S, 145°20’ 23’’ E, 23 August 2008; K. & D. Kalb (herb. Kalb 41459, 41460); Daintree National Park: Mossman Gorge; in a ± pristine, dense tropical rainforest with Cerbera floribunda, Exocarpos latifolius, Livistona spec. , etc. 50 m, 16°28’26’’ S, 145°20’11’’ E, 25 August 2008, K. Kalb (herb. K. Kalb 41463).

Figures

FIGURE 5. A. Coenogonium convexum (KK 41133), transverse section through the crustose thallus showing the corticiform layer, scale 15 μm. B. Thallodiscs laying upside down on the thallus of Coenogonium isidiiferum (KK 41459), scale 0.3 mm, scale of inlet 0.1 mm. C. Coenogonium luteum (Schumm 8577), exciple coloured with lactophenol-anilinblue, scale 20 μm. D. Coenogonium leprieurii (RAMK 027804 b), ascus tip stained permanently blue with Lugol‘s solution. E. and F. Coenogonium aff. borinquense (KK 38577) showing different arrangement of ascospores within the asci of the same section, scales 5 μm and 10 μm. G. Coenogonium subborinquense (KK 38820), irregular shaped pycnidia, scale 0.2 mm. H. Coenogonium subluteum (RAMK 004684 b), hymenium stained with Lugol‘s solution; after some time, the upper part still remains blue while the lower part has turned red brown. I. Coenogonium luteum (Schumm 8577), hymenium stained with Lugol‘s solution; after some time, the whole hymenium has turned red brown. J. Conogonium barbatum (RAMK 004687), habitus, filamentous thallus projecting from the margin of a leaf, scale 1.5 mm.

FIGURE 7. Habitus photographs of Coenogonium species.A. Coenogonium interplexum (RAMK 027802), showing a young substipitate apothecium (upper part), scale 0.4 mm. B. Coenogonium isidiatum (KK 24025), scale 2 cm. C. Coenogonium isidiiferum (KK 41459), marginal part of thallus, scale 0.4 mm. D. Coenogonium isidiiferum (KK 41459), exfoliating thallodiscs, leaving ± round holes in the thallus, scale 0.2 mm. E. Coenogonium leprieurii (RAMK 27804), scale 1 mm, scale of inlet 0.5 mm. F. Coenogonium luteum (KK 24052), scale 1 mm.